The thesis presents a historical study of the Enlightenment project for a Science of Man which takes its perspective from the 20th century philosophical 'death of man'. From the contemporary move against humanistic ideals associated already from the 1930's exemplified contrasting interpretations over an Enlightenment Science of Man and its ambitions. In the 1960's Michel Foucault's pivotal approach gave this dispute the perspective of the 'death of man', which this thesis frames in relation to his reading of Kant. This forms a perspective from which to examine Kant's positive ambitions, as Foucault saw them extending beyond Critique. But a second perspective is taken up through what Gilles Deleuze ascribed to an empiricist tradition subjugated under a vitalism. This is indicated by the 'age of Bichat', the French medical tradition which Deleuze contrasted with Foucault's 'rarefied form of positivism'. A genealogical history of the Science of Man frames these as alternative models to a critique of reason, two perspectives derived of the Enlightenment project. The 'age of Bichat' is understood around the French Enlightenment discourse on vitalism modelled on a post-Cartesian concept of the body. This gave the positive ambitions for early 19th century Positivism explored through Saint Simon's 'concept of labour' and August Comte's epistemological critique, intended as substitute for an older Enlightenment model. However, this becomes further complicated by the new positive paradigm of experimental medicine. The effect, during the early Third Republic, was to re-orientate the philosophical perspective on the older project for a Science of Man. This served Henri Bergson's critique of Positivist historical formations, but also the neo-Positive model of Emile Durkheim and the ambition for an autonomous new science that delimits a collective 'order of things'. The dilemma was legitimating vital norms in a modern society. This genealogy situates these as perspectives seen through the 18th century Science of Man from which the vital and the positive remained elements historically resistant to being the determinable object of study.